The ability to control the shape of a beam of light emitted by a light source is desirable in many applications ranging from general lighting to special lighting applications. Some examples are video flash, with beam shaping in combination with zooming, spot lights, flash lights, interior lights, head lamps and interior lamps.
Conventionally, this beam shaping is achieved by mechanical beam shaping devices, such as mechanically controllable zoom lens arrangements. Recently, more compact beam shaping devices, utilizing the controllable properties of liquid crystal materials have been developed. An example of such a beam shaping device is disclosed in EP 0 578 827, where a liquid crystal light regulating plate scatters a desired amount of light emitted from a light source. By changing a control power source voltage applied for controlling the light scattering rate, it is possible to continuously diverge the light beam passing through the beam shaping device to thereby change the brightness of the illuminating light.
Although being relatively compact and providing electrically controllable beam shaping, the beam shaping device disclosed in EP 0 578 827 suffers from loss of light due to backscattering Moreover, the random scattering of this device is not well suited for controlled beam-shaping.